Unfortunately, I realized I couldn't switch due to some restrictions from mobstac leaving me with the option of re-subscribing or my site gets deleted from mobstac's server.

I decided to re-subscribe to see if I can switch when I have an active plan and it worked. My subscription will expire tomorrow but I have been able to successfully downgrade my account to the free plan yesterday.

So, if somehow you still want to be using mobstac but don't want to keep paying for their service, follow the steps below in switching to the free plan.